SPECIFIC RESEMBLANCES. 121 



narrowed bases of the distinct pinnules, the more slender upper, con- 

 fluent pinnules and the closer nervation. There is perhaps no generic 

 difference between the two plants. Alethopteris maxima, Andr., 1 as seen 

 in a specimen from Rushville, Ohio, determined by Professor Lesquereux, 

 is an alethopterid, though the difference between it and Protoblechninu 

 may not be of generic rank. Still earlier in the geologic series a form 

 perhaps somewhat similar existed in the Alethopteris ingens, Daws., 2 the 

 pinnules of which, more than one inch in width and three inches or more 

 in length, have the Bauxites nervation, or the J. discrepans, Daws., 3 both 

 from the middle Devonian of St. Johns, New Brunswick, the long, ribbon- 

 like, open pinnules of which are united, however, by a narrow decurrent 

 wing. So far as the form and development of the pinnules, and to some 

 extent the nervation, is concerned, a closer resemblance obtains in the 

 cases o£ Pseudodanxupxix reticulata, Font., 4 from the Upper Trias at Clover 

 Hill, Virginia, or the forms of Tseniopteris munsteri, Goepp. (Angiopteris, 

 fide Schenk), from the Lias of Bornholm. 5 Tin; upper pinnules of the 

 Virginia species are united, as figured by Fontaine, while the lower ones 

 are long, ribbon-like, and distinctly and nearly equally rounded at the 

 base, as in our plant from Missouri. Perhaps its nearest affinity is, how- 

 ever, with the Tie nioptcr is jejunata of Grand Fury,''' from the Upper Car- 

 boniferous and Permian of France. In this species, of which the upper 

 parts of the pinnae are, I believe, unknown, the pinnules are sometimes 

 short-pedicelled, the lamina thin, and the nerves generally more oblique 

 near the midrib and more regular, as figured, in passing to the margin 

 than in our species. 7 Inform the Missouri species is also close to certain 

 species referred by Stur 8 and Zeiller 9 to Desmopteris, Stur, which has a 

 somewhat different nervation, though it appears to be allied to the 

 alethopteroid gr< >up. 



Generic Reference. — In the characters of the rachis with its thickened, 

 sulcate, center and marginal laminae, in the origin of the nervils in the 

 median canal of the pinnule, the ribbon-like lamina of which is rounded 

 at the base where it overlaps the rachis, and, to a less extent, in the 

 character of the nervation, the middle pinnules (figure 5) of our species 

 are referable to Tseniopteris or to Danseites, according to one's interpreta- 



1. Geol. Surv. Ohio, Pal. II, p. 421, pi. I, figs. ::, Za-b. 



2. Foss. PL, Dev. Sil. Form., Can., pi. xviii, tig. 206, i>. 54. 



3. Op. cit., p. 54, figs. 203-205. 



4. Older Mcs. Fl., U. S. Geol. Surv. Monogr., vi, p. 59, pi. xxx, figs. 1-4. 



5. Bartholin: Botanisk Tidsskr., vol. xviii, lift, i, Kjobenhavn, L892, p. ■£',, pi. ix, fig. 9. 



0. Fl. Carb. Loire, p. 121 ; Zeiller, Fl. 1'oss. Commentry, pt. 1, p. 280; All., pi. xxii. figs. 7-!); Zeiller, 

 Fl. foss. Autun, Epinac, p. 102, pi. xii, fig. 6. 



7. The nervation seen in the figures of T. missouriemis is drawn with fidelity in detail from the 

 originals. 



8. Carbon. -Fl. Schatzlarer Sch., i. See D. belgiea, Stur. p, isi, pi. Hi, rigs. 7-9. 



9. Fl. foss. Valenciennes, p. 21G, pi. xxxviii, figs. 3-5. See Ettingshausen: fl. Radnitz, p. 1", pi 

 xvi, figs. 2-4. 



